Reason for yawning is infectious – Yawning is seen as opening of mouth as wide as we can with sometimes watering eyes and noses and putting both hands above our head during inhaling. Human yawns from their earliest days, even babies do it inside the womb. Animals such as snakes, fish, dogs, and cats also do it. Expects say that real function of yawning is to increase the rate of blood flow to the skull while stretching the jaws. The air inhaled changes the temperature of blood flow bringing cooler blood to the brain. Experts say that yawning is extraordinary infectious in the sense and the other person on person’s sitting near yawning person starts yawning. Even thinking of yawning causes yawns. When we see somebody yawning we get chain reaction of biology and may start yawning. So it is contagious or infectious.

Reason for laughter is infectious – So far laughing is concerned studies have shown that laughing has been passed on to human from our ancient primate ancestors. Laughter increases bonding between people laughing occurs due to various reasons such as jokes or seeing funny things or videos. But whenever we laugh at somebody’s shortcomings or ridicule somebody we cast someone out. Human emotions are highly contagious or infectious and it is true for laughter also. One person’s laughter is soon shared by another due to strong emotions synchronize the brain activity of different individuals. The brain also responds to the sound of laughter and preps the muscles in the face to join the gladness. So, laughter is infectious.